An HEV is a vehicle that has a vehicle powertrain system for propulsion that consists of at least one electric motor or electric machine in combination with at least one other power source. Typically, the other power source is a gasoline or diesel engine. There are various types of HEVs depending on how the electric motor(s) and other power source(s) are combined with one another in order to provide propulsion for the vehicle, including series, parallel and compound HEVs, including those having electrically variable transmissions (EVTs) which provide for continuously variable speed ratios by combining features from both series and parallel HEV powertrain architectures.
The development of new HEV powertrain systems and architectures also facilitate and necessitate the development and implementation of novel vehicle operating and diagnostic methodologies which are adapted to utilize and assess novel features of these systems, including assessing the status and availability of certain systems, subsystems and components to perform their intended function. This information is particularly desirable in conjunction with restarting of the HEV from a shutdown or “key-off” condition to a restart or “key-on” condition, because on key-off much of the system is powered off in order to conserve the state of charge of the energy storage system, such as a battery pack or array. As such, changes in the status of many of the vehicle systems, subsystems and components are unknown, and it is preferred to test certain of them in order to verify their operational status prior to utilization of the powertrain system. For example, if maintenance is performed on the vehicle during the key-off condition, it may be desirable to ensure that cetain of the vehicle systems, subsystems and components are working properly prior to returning the vehicle to service. One such item for which information about the status and availability is desired is the electric motor(s) used for propulsion of the vehicle with respect to its integrity or ability to produce the desired output torque for propulsion of the HEV powertrain system.
Therefore, it is very desirable to develop a method for testing the electric motor(s) used for propulsion in an HEV powertrain system prior to utilization of the system in order to determine whether it is capable of producing the desired output torque.